In an electronic data storage and retrieval system, a transducing head typically includes a writer for storing information on a storage medium and a reader for retrieving that information from the storage medium. In a magnetic data storage system, the reader typically consists of two shields and a magnetoresistive (MR) sensor positioned between the shields. Magnetic flux from the surface of the storage medium causes rotation of the magnetization vector of a sensing layer of the MR sensor, which in turn causes a change in electrical resistivity of the MR sensor. This change in resistivity of the MR sensor can be detected by passing a current through the MR sensor and measuring a voltage across the MR sensor. External circuitry then converts the voltage information into an appropriate format and manipulates that information as necessary.
In magnetic recording, it is desirable to improve the areal density at which information can be recorded and reliably read. This desire has led to a trend toward, for example, shorter bit length along a magnetic recording track and a shrinking track width to provide higher density recording. Currently, readers are based on multilayers of magnetic and non-magnetic material that produce giant magnetoresistance (GMR). These readers are biased with an electrical current that predominantly flows in the plane (CIP) of the thin film multilayer. Similar designs based on GMR and tunneling magnetoresistance (TMR) have the bias current flow perpendicular to the plane (CPP) of the multilayer. Under high areal densities, CIP-GMR readers can have difficulty producing a large enough read-back amplitude. Additionally, CPP-GMR and TMR readers can have large amounts of noise. In addition, a result of narrowing track width is a loss in signal-to-noise ratio (SNR) during readback, as well as, increased intertrack interference (ITI). In high-density, narrow trackwidth systems ITI degrades the error-rate performance of current readers due to the noise that is picked up from neighboring tracks that are not being read.